Thermocouple probes useful for measuring the temperature of a surface are well known. Such devices are typically hand-held having a support on one end from which extends a suitable thermocouple element. Thermocouple probes are especially useful in measuring the temperature of a moving surface such as, for instance, a rotating fuser roll of an electrophotographic copying machine.
U.S. Pat. No. 3,395,050 to Senbokuya illustrates a prior art rapid response thermocouple probe. The reduced thickness of the element, necessary for rapid response, greatly reduces its durability. Accordingly, the thermocouple element, which is formed as an arcuate strip, is permanently mounted on a support and is formed as a unitary structure with the leads. This construction has several disadvantages. First, upon wear of the thermocouple element, the usefulness of the entire probe is destroyed and a new probe must be acquired. Secondly, the complexity of the manufacturing process is increased due to the need to assemble and weld the various parts forming the unitary structure.
U.S. Pat. No. 4,279,154 to Nakamura discloses a thermocouple probe having an arcuate thermocouple element, similar to that disclosed by Senbokuya, an element support means such as that disclosed by Senbokuya, and additionally a layer of a slippery, electrically insulated material disposed over the surface of the thermocouple element to prevent an ungrounded junction between the thermocouple element and the surface to be measured, and also to reduce wear of the thermocouple element. Although extending the life of the thermocouple element, the disclosure of this patent does not eliminate the problem that, once wear does occur, the entire thermocouple probe must be replaced, not just the thermocouple element. Moreover, it has other problems of the type noted above for Senbokuya.
U.S. Pat. No. 3,416,973 to Benzinger discloses a thermocouple apparatus in which the entire apparatus may be disconnected from the leads and discarded. The replaceability of the thermocouple element to eliminate the need to discard the entire apparatus is clearly not within the contemplation of Benzinger. Moreover, it is apparently too massive to provide rapid response.
U.S. Pat. No. 4,595,020 to Palti discloses a thermocouple probe whose usable life span is shorter than the time it takes to wear out or break the thermocouple element. This patent, therefore, does not address the problem of wear of a rapid response thermocouple element when the usable life of the thermocouple probe is desired to be longer than that of the element.
There remains a present need for a rapid response thermocouple probe having a simple, durable and replaceable thermocouple element, thus eliminating the need to discard the entire thermocouple probe upon wear or breakage of the element.